Bishop Sheen Hospital is evaluating a lease arrangement for its ambulance fleet. The total value of the lease is $620,000. The hospital will be making equal monthly payments starting today.

a. What is the monthly interest rate if the lease payments are $50,000 per twenty-four months?

b. What is the monthly interest rate if the lease payments are $50,000 per thirty-six months?

c. What is the monthly interest rate if the lease payments are $60,000 per month for thirty-six months?